1. Field of the Invention
This invention relates to a vibration isolation device for efficiently decoupling an experimental instrument or source of vibration from its environment at frequencies above an extremely low resonant frequency.
2. Description of the Prior Art
There is considerable prior art relating to the subject of decoupling sources of vibration from the environment or, conversely, isolating experimental instruments and the like from vibration in their environment. In the former case, it is often desired to separate a prime mover such as an electric motor from its environment so that vibration generated by the prime mover is absorbed and is not communicated to associated equipment. In the latter case, it is often desired to decouple an experimental apparatus, such as a delicate laboratory instrument, from its environment so that vibration in the environment does not interfere with the experimental measurement being made.
Various devices have been provided to address these problems. A first class of devices are found in references disclosing highly rigid table tops intended to be supported on supports exhibiting relatively low resonant frequency. See U.S. Pat. No. 4,645,171 to Heide, and brochures published by Newport Scientific Company and other manufacturers of such equipment.
The art has also attempted to develop active-servo vibration isolation systems, that is, in which vibration is sensed and opposed by an actively driven servo system. See generally Greene U.S. Pat. Nos. 4,730,541 and 4,850,261; Pepi U.S. Pat. No. 3,730,473; Abrams et al U.S. Pat. No. 4,546,960; Jacot et al U.S. Pat. No. 4,848,525; and Sandercock U.S. Pat. No. 5,000,415.
Generally related prior disclosures include U.S. Pat. No. 3,679,592 to Bach et al showing a vibration isolation structure including opposed plates supported by interlocking flexible fluid filled containers, and U.S. Pat. Nos. 3,415,478 and 3,429,544, both to Williams for air tables.
Also generally pertinent is U.S. Pat. No. 3,672,473 for a pendulum system issued to Verhagen. The Verhagen patent shows a pendulum system for "stabilization purposes" or for use as a very low resonant frequency oscillator for measurement of wave energy in the sea or the like; see column 3, lines 20-25. The Verhagen pendulum system includes a pendulum suspended in a liquid filled volume, the density of the pendulum being controlled to be closely comparable to that of the liquid to provide an oscillation period of between 75 to 150 seconds; that is, the pendulum has a very low resonant frequency between 0.0133 and 0.00666 Hz. However, even assuming the Verhagen pendulum system achieves as stated a very low resonant frequency, and thus would be substantially unaffected by high frequency vibration, this system cannot be adapted for supporting experimental apparatus or motors.